In the food and beverage processing industry, the cleaning, filling and labeling of bottles are carried out automatically. The bottles are moved from operation station to operation station on belt conveyors. Since the use of plastic conveyor belts is increasing in the food and beverage industry, there is a need for aqueous-based lubricants that provide excellent lubricity and without showing any detrimental effects on the plastics.
Very little is known about aqueous-based lubricants for plastic conveyor belts, tracks or chains. The type of plastic conveyor system used in the industry is, for example, that described in U.S. Pat. No. 4,436,200.
Lubricants are well known in metal conveyor systems and the role of nonionic surfactants in such systems has been described in U.S. Pat. Nos. 3,372,117 and 4,414,121. Both of these patents describe the use of a block copolymer of ethylene oxide and propylene oxide as a nonionic surfactant in combination with other ingredients for a metal coating lubricant composition for metal conveyor systems.
Nonionic surfactants have also been used in combination with anionic or cationic surfactants in preventing stress cracking of polymers as described in U.S. Pat. No. 3,352,787.
The lubricant described in U.S. Pat. No. 4,436,200, which is directed to plastic conveyor belts, is a dry lubricant made up of fibers imbedded in the thermoplastic. These fibers are uniformly disbursed and consist of tetrafluoroethylene monofilamentous fibers.
It is has now been discovered that the use of block copolymers of ethylene oxide and propylene oxide, commercially known as Pluronics.RTM., manufactured by BASF, can be used as a key ingredient in an aqueous lubricant composition for plastic conveyor systems. Such lubricants show superior lubricity and outperform present marketed lubricants for metal conveyors.